1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copying machine, a facsimile, a printer, a multifunctional image forming apparatus having a plurality of image forming functions, and other similar devices, and more particularly to the image forming apparatus having a ventilating device that can effectively cool heated components and remove ozone produced in the apparatus.
2. Discussion of the Background
In a writing device to be used in an image forming apparatus, beam light such as laser beam light is emitted from a light source based on a signal of a read image. The laser beam light is deflected by a polygon mirror. The deflected light is then led to a surface of an image bearing member through an fxcex8 lens and a mirror to form an image on the surface thereof.
A scanning optical component in the writing device, such as the fxcex8 lens and mirror are formed of a plastic or a glass. Because of a growing request for a cost reduction and with the development of processing techniques, an increased number of components formed of a plastic are used in recent years.
However, the components formed of a plastic expand and become deformed according to a rise in a surrounding temperature, which may generate an image distortion. Recently, a risk of the generation of the image distortion is increased because the temperature in the apparatus tends to increase quickly due to a higher rotating speed of the polygon mirror and an increased heating value of a fixing device.
In addition, a housing made of an aluminum die casting, which has a high thermal conductivity, is frequently employed for the writing device to assure accuracy, high rigidness, and resistance to vibration. Thus, heat from a heat source is well conducted to the scanning optical system.
In Japanese Patent Laid-Open Publication No. 5-5851 and Japanese Utility Model Laid-Open Publication No. 3-54913, an image forming apparatus is discussed in which ventilation of a surrounding of a writing device is improved to suppress an increase in a temperature, thereby preventing an occurrence of an image degeneration.
However, in the above-described image forming apparatus, great attention is paid to cooling the polygon mirror. A principal objective is to protect the polygon mirror itself. Thus, when scanning optical components, such as the fxcex8 lens and mirror are formed of a plastic, a thermal expansion of these components is not sufficiently suppressed.
The present invention has been made in view of the above-mentioned and other problems and addresses the above-discussed and other problems.
The present invention advantageously provides a novel image forming apparatus having a ventilating device for effectively cooling a writing device to prevent scanning optical components disposed in the writing device from being excessively heated, thereby preventing a thermal expansion of the components in the writing device. Thus, a generation of an image distortion and an occurrence of image degeneration are prevented. In addition, an airflow that cooled the components removes ozone produced in the apparatus. According to an example of the present invention, the image forming apparatus includes a writing device. Upper and lower ducts are provided to the writing device having a housing therebetween to form an outside-air flowing path on and beneath the writing device. Outside-air intaken by an air intake fan flows through the upper and lower ducts separately. Scanning optical components, such as an fxcex8 lens, and a mirror formed of a plastic are disposed in the writing device.